But Zia's visit was anything but routine. As the family conversed, Zia called the mobile phone of one of six men waiting outside the house and went to the front door to let them in.

The men were killers, hired by Zia from his home province of Khyber Pakhtunkhwa, and they had come to the Pakistani capital on a promise: 2.5 million rupees ($A24,000) for killing Nazia and her entire family.

In the quiet cloistered streets the seven men did their job without anyone noticing, murdering Nazia, her husband, Amir Khan, and their three children, Romana, 17, Adam, 14, and Haider, 7.

Khan, the head of the family and whose money and property they sought, was killed first, strangled to death as his family watched on. Then his eldest two children and wife. They killed Haider last. As they had with the other family members, they tied his hands and feet with rope and taped his mouth. Then they strangled him to death with wire.

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''I could not let him live. He knew me and we had played together, and he could identify me,'' Zia tells Fairfax Media.

Police believe the crime was almost uncovered in its commission. A servant to the Khan family, Asghar, interrupted the men. He was stabbed to death. Zia told police Asghar was part of the plan, promised 500,000 rupees ($A4800) to keep anyone else from entering the house. He was killed because he could identify them.

Khan and his children's bodies were dumped on the side of the Grand Trunk Road to Lahore. His wife and servant's bodies were left in bushes in a nearby suburb.

A week since the crime, Zia sits barefoot in an Islamabad police cell. His hands are in cuffs behind his back, tied by a chain to the belt of a police officer who stands over him. He sits with a red sash tied around his eyes as a blindfold.

Zia is unemotional as he explains why he killed an entire family.

''It was my plan I came up with 15 days ago,'' he says. ''I was facing financial crisis and this was the easiest solution to get money.''

Khan and his family were dual Australian-Pakistani citizens. They lived in suburban Glen Waverley from 2000 to 2005 and still had property and bank accounts in Australia. Khan had visited friends in Cranbourne last year.

By Pakistani standards the Khans were wealthy, and ostentatiously so. Khan owned more than a dozen homes in Bahria town and drove a 2013 four-wheel-drive vehicle. His wealth had brought attention, and threats, before. In Pakistan, a police station is not a threatened man's first port of call, a gunsmith is. Khan had recently purchased a Kalashnikov.

As the nephew of Khan's wife, Zia and his family stood to inherit much of Khan's land and wealth. Zia says he bore no grudge against Khan. His uncle had always been generous to him. ''There was no issue between us, between me and Mr Amir. He was a gentleman.''

Twenty-seven-year-old Zia speaks excellent English and has an MBA. He seemingly had good prospects in a country where bright young men from the country can make their fortunes in the city. But his case is an insight into the intense familial pressures that exist in parts of Pakistan, particularly in his ancestral home of Khyber Pakhtunkhwa.

Young men are given opportunities - families make enormous sacrifices to give them a chance at education, travel and employment - but there is also obligation. They are expected to do well and to give back. There is prestige and honour in being a good provider.

Zia's ticket was a petroleum business that had foundered in the past two years, like so many other enterprises in Pakistan's wretched economy. Zia had overextended his credit, the bills were coming in and he saw no other way to pay them.

''I was still paying the rents but there was no money. I was in serious financial crisis.''

For all his intelligence and ambition, Zia was a clumsy criminal. CCTV footage shows him in the neighbourhood on the night of the murder and his mobile phone records place him at both places where the bodies were dumped.

After arriving at the Islamabad hospital to identify his family members' bodies, and attending their funeral, Zia disappeared, turning off his phone as police sought him for questioning.

When he was finally found, he was evasive and contradictory in his answers. He was formally arrested last Sunday night and he confessed to the crime. Three of his hired assassins have also been arrested, and police are confident of finding the others.

Zia says he expects - even wants - the death penalty. ''I cannot face anyone now, not my family, not my friends. I can't be forgiven … I will ask the judge for the death penalty.''